You're spot on. I try to keep up with everything just for fun and there is very little information on professional internships out there.
Here are a couple of things I can think of off the top of my head as to why:
1) There are less positions than the CP so your overall # of Pi participants is much smaller. In turn this would make the potential blogger pool much smaller.
2) Each PI is very unique (Guest Relations is way different from something in Marketing which is way different than something in Animal Science) . It would be very difficult to do anything that is a blanket for the PI program.
3) Their application process is so simple, yet so drawn out. You know, you just submit your stuff and maybe you get an interview and maybe you don't....weeks later. Then you may have a second interview or maybe not. There aren't any presentations or anything that is ongoing. There really isn't anything to talk about until the interviews start happening and people start finding out if they got in or not. then when that happens, there isn't much time between then and when the pi begins.
4) People just don't want to blog about it. Some PI's only have one or two openings in it. So if someone is actively blogging about their job, it wouldn't be too difficult for The Man to figure out who the person is. Plus there is the whole layer of confidentiality and all of that. Even if one wanted to blog about that meeting you were just in where about a new merchandise location was talked about, is anyone really that dumb to put that on their personal blog and would think that it wouldn't get sniffed out by the massive disney online fan community and thus get found out by The Man?
The College Board here on DIS is where I've seen the most activity regarding PI's.